1. Field of the Invention
The invention relates to food processing and to methods and systems for particle size reduction of edible starting materials. Specifically, the invention utilizes dry milling for the particle size reduction with either an unreactive ambient atmosphere circulating in a closed loop, or an increased temperature atmosphere. The methods and systems of the present invention may be used to produce novel chocolate products free of off-notes.
2. Description of the Related Art
The smooth mouthfeel of chocolate depends to a large extent on the size of the chocolate solids contained in a recipe. Large particles, exceeding 50 to 60 microns, for example, impart a gritty texture not normally viewed as acceptable. This requirement makes particle size reduction a critical step in chocolate making.
The traditional method of making chocolate employs a 2, 3, or 5 roll refiner for reducing the size of a paste containing sugar, milk, chocolate liquor and fat. Cocoa butter, milk fat, or a combination of these, may be used depending on the desired recipe. Agitated ball mills, stone mills and refiner conches have also been used. All of these wet grinding apparatus are known to be labor intensive to operate and expensive to maintain.
In recent years, as consumers have demanded lower fat content chocolates, the roll refiner has met with limitations. International Application WO 99/45789, incorporated by reference herein in its entirety, discloses using particle size control to obtain chocolates having fat content below about 25 weight percent.
Dry milling of chocolate ingredients in an air-jet mill, air classifying mill, hammer mill, or the like, permits improved particle size control. Even for conventional recipes having greater than 25 percent fat, dry milling provides rheological advantages, as disclosed in V. Eynck, xe2x80x9cDry Grinding and Mixing of
Compound Coatings,xe2x80x9d 43rd P.M.C.A. Production Conference (1989), pp. 35-38.
In view of the foregoing, it would be desirable to move toward dry milling of chocolate and chocolate precursors from the standpoint of efficiency, cost and finished product quality.
However, dry milling has been found to lead to loss of desirable flavors and in many cases to the development of off-notes. These off-notes are flavors not normally found in chocolate and generally seen as undesirable. The inventors have discovered several off notes arising in the dry milling of chocolate ingredients, including xe2x80x9cmetallic,xe2x80x9d xe2x80x9cfishy,xe2x80x9d xe2x80x9ccardboard,xe2x80x9d xe2x80x9cwet-dogxe2x80x9d and xe2x80x9crancidxe2x80x9d notes that can carry over to chocolate made from these ingredients. The extent of the off-note intensity has been linked to the source of the raw materials. Dairy powders derived from milk of pasture-fed cattle appear to have a greater propensity to develop these undesirable flavors. This has severely limited the use of dry milling for widespread chocolate manufacture. Without wishing to be bound by any theory of what is responsible for these phenomena, it is believed that exposing nonfat milk, whole milk, lactose, sugar (sucrose), cocoa, flavorings and combinations thereof to attrition in combination with high volumes of air is sufficient to create the objectionable off-notes.
The solution to the problem of off-notes has proven to be elusive. Addition of very effective natural and synthetic anti-oxidants including TBHQ, BHT, BHA, and vitamin E to a dry mix of powders prior to milling has no significant impact on the off-note generation.
International Application WO 93/19629 discloses a method of preserving foods using noble gases. With regard to chocolate, the method entails contact, and preferably the saturation of, chocolate with a noble gas such as argon, at any stage, and preferably at every stage of chocolate production. The above International Application does not disclose or suggest dry milling of chocolate ingredients.
This invention is directed to methods and systems for manufacturing powdered edibles free of off-notes. The invention allows for the integration of dry milling into the production of chocolate in a continuous process without using a roll refiner.
A method according to one embodiment of the invention comprises feeding an edible composition comprising milk powder and containing less than about 15 percent fat through a dry mill in continuous contact with air having a temperature between about 65xc2x0 C. and about 120xc2x0 C. to produce reduced-size particles, and recovering the reduced-size particles. In a more preferred embodiment, the exit temperature of the dry mill (dry mill exit temperature) is between about 68xc2x0 C. and about 85xc2x0 C. In the most preferred embodiment, the dry mill exit temperature is between about 70xc2x0 C. and about 75xc2x0 C.
In a preferred embodiment, the dry mill used with the system is an air classified mill which reduces the particle size of the starting material to between about 10 and about 60 microns. After particle size reduction, the particles may be combined with chocolate liquor, cocoa butter and other materials to make chocolate. When referring to particle size herein, the measurements were taken using a micrometer.
In preferred chocolate-manufacturing embodiments, the starting material comprises a milk powder and contains between about 0.08 weight percent and about 12 weight percent fat, and the particles obtained are free of off-notes. In preferred embodiments the starting material contains between about 10 and about 12 percent fat.
In another embodiment, the system of this invention includes a closed gas circulation loop containing a circulating gas; a fan to circulate gas continuously throughout the closed gas circulation loop; a source of substantially unreactive gas operatively connected to the gas circulation loop; a damper to control the addition of the substantially unreactive gas to the circulating gas; a source of edible starting material; a dry mill operatively connected to the source of edible starting material to reduce the particle size of the edible starting material to form product particles; and a gas-solid separator to recover the product particles from the circulating gas. In a preferred embodiment, the edible starting material and the product particles are continuously contacted with said circulating gas.
A preferred method of making chocolate using the above-described closed system comprises providing a substantially unreactive gas to the closed system, feeding a composition comprising chocolate liquor, powdered milk product and sugar and containing less than about 15 percent fat through a dry mill in contact with the circulating gas to produce particles, recovering the particles from the circulating gas, and combining the particles with cocoa butter, additional chocolate liquor and other ingredients to make chocolate.